Microelectromechanical systems1

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Microelectromechanical systems

Introduction

Microelectromechanical systems (MEMS) are smallintegrated devices or systems that combine electrical andmechanical components. They range in size from thesubmcrometer (or sub micron) level to the millimeter level,and there can be any number, from a few to millions, in aparticular system. MEMS extend the fabrication techniquesdeveloped for the integrated circuit industry to addmechanical elements such as beams, gears, diaphragms,and springs to devices.

Examples of MEMS device applications include inkjet-printercartridges,acceleratometers , miniature robots,microengines, locks, inertial sensors, microtransmissions,micromirrors, micro actuators, optical scanners, fluidpumps, transducers and chemical pressure and flow sensors.New applications are emerging as the existing technology isapplied to the miniaturzation and integration of conventionaldevices.

These systems can sense, control, and activate mechanicalprocesses on the micro scale, and function individually or inarrays to generate effects on the macro scale. The microfabrication technology enables fabrication of large arrays ofdevices, which individually perform simple tasks, but incombination can accomplish complicated functions.

MEMS are not about any one application or device, nor arethey defined by a single fabrication process or limited to a

few materials. They are a fabrication approach that conveysthe advantages of miniaturization, multiple components, andmicroelectronics to the design and construction of integratedelectromechanical systems. MEMS are not only aboutminiaturization of mechanical systems; they are also a newparadigm for designing mechanical devices and systems.


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Microelectromechanical systems (MEMS) (also written as micro-

electro-mechanical,MicroElectroMechanical or "microelectron . andmicroelectromechanical systems")are separate and distinct from the hypothetical vision of molecular

nanotechnology or molecular electronics.MEMS are made up of components between 1 to 100 micrometres insize (i.e. 0.001 to 0.1 mm) and MEMS devices generally range in sizefrom 20 micrometres (20 millionths of a metre) to a millimetre. Theyusually consist of a central unit that processes data, themicroprocessor and several components that interact with the outsidesuch as microsensors

II. Historical Background

The invention of the transistors at Bell TelephoneLaboratories in 1947 sparked a fast-growing microelectronictechnology. Jack Kilby of Texas Instruments built the firstintegrated circuit (IC) in 1958 using germanium (Ge)devices. It consisted of one transistor, three resistor, andone capasitor. The IC was implemented on a sliver of Gethat was glued on a glass slide. Later that same year RobertNoyce of Fairchild Semiconductor announced thedevelopment of a planer double diffused Si IC. The

complete transition from the original Ge transistors withgrown and alloyed junctions to silicon (Si) planar double-diffused devices took about 10 years. The success of Si asan electronic material was due partly to its wide availabilityfrom silicon dioxide (SiO2) (sand), resulting in potentiallylower material costs relative to other semiconductors.

Since 1970, the complexity of ICs has doubled every two tothree years. The minimum dimension of manufactured

devices and ICs has decreased from 20 microns to the submicron levels of today. Current ultra-large-scale-integration(ULSI) technology enables the fabrication of more than 10million transistors and capacitors on a typical chip.

IC fabrication is dependent upon sensors to provide inputfrom the surrounding environment, just as control systems


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need actuators (also referred to as transducers) in order tocarry out their desired functions. Due to the availability ofsand as a material, much effort was put into developing Siprocessing and characterization tools. These tools are now

being used to advance transducer technology. Today's ICtechnology far outstrips the original sensors and actuators inperformance, size, and cost.

Attention in this area was first focused on microsensers (i.e.,microfabricated sensor) development. The first microsensor,which has also been the most successful, was the Sipressure sensor. In 1954 it was discovered thatthe piezoresistive effect in Ge and Si had the potential to

produce Ge and Sistrain gauges with a gauge factor (i.e.,instrument sensitivity) 10 to 20 times greater than thosebased on metal films. As a result, Si strain gauges began tobe developed commercially in 1958. The first high-volumepressure sensor was marketed by National Semiconductor in1974. This sensor included a temperature controller forconstant-temperature operation. Improvements in thistechnology since then have included the utilization of ionimplantation for improved control of the piezoresistor

fabrication. Si pressure sensors are now a billion-dollarindustry

Around 1982, the term micromaching came into use todesignate the fabrication of micromechanical parts (such aspressure-sensor diaphragms or accelerometer suspensionbeams) for Si microsensors. The micromechanical parts werefabricated by selectively etching areas of theSi substrate away in order to leave behind the desiredgeometries.Isotropic etching of Si was developed in theearly 1960s for transistor fabrication. Anisotropic etching ofSi then came about in 1967. Various etch-stop techniqueswere subsequently developed to provide further processflexibility.


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These techniques also form the basis of the bulkmicromachining processing techniques. Bulk micromachiningdesignates the point at which the bulk of the Si substrate isetched away to leave behind the desired micromechanical

elements.Bulk micromachining has remained a powerfultechnique for the fabrication of micromechanical elements.However, the need for flexibility in device design andperformance improvement has motivated the developmentof new concepts and techniques for micromachining.

Among these is the sacrificial layer technique, firstdemonstrated in 1965 by Nathanson and Wickstrom in whicha layer of material is deposited between structural layers for

mechanical separation and isolation. This layer is removedduring the release etch to free the structural layers and toallow mechanical devices to move relative to the substrate.A layer is releasable when a sacrificial layer separates itfrom the substrate. The application of the sacrificial layertechnique to micromachining in 1985 gave rise to surfacemicromachining, in which the Si substrate is primarily usedas a mechanical support upon which the micromechanicalelements are fabricated.

Prior to 1987, these micromechanical structures were limitedin motion. During 1987-1988, a turning point was reached inmicromachining when, for the first time, techniques forintegrated fabrication of mechanisms (i.e. rigid bodiesconnected by joints for transmitting, controlling, orconstraining relative movement) on Si were demonstrated.During a series of three separate workshops onmicrodynamics held in 1987, the term MEMS was coined.Equivalent terms for MEMS are microsystems (preferred inEurope) and micromachines (preferred in Japan)

MEMS description

MEMS technology can be implemented using a number ofdifferent materials and manufacturing techniques; the choice


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of which will depend on the device being created and themarket sector in which it has to operate

Materials for MEMS manufacturing


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Siliconslicon is the material used to create most integrated circuit used in

consumer electronics in the modern world. Theeconomes of

scale, ready availability of cheap high-quality materials andability to incorporate electronic functionality make siliconattractive for a wide variety of MEMS applications. Silicon alsohas significant advantages engendered through its materialproperties. In single crystal form, silicon is an almostperfecthookeanmaterial, meaning that when it is flexed thereis virtually nohysterasisand hence almost no energydissipation. As well as making for highly repeatable motion, thisalso makes silicon very reliable as it suffers very

littlefatigueand can have service lifetimes in the range ofbillions totrillionsof cycles without breaking. The basictechniques for producing all silicon based MEMS devicesarederositionof material layers, patterning of these layersbyphotolithography and then etching to produce the requiredshapes.


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Polymers

Even though the electronics industry provides an economy of scale

for the silicon industry, crystalline silicon is still a complex and

relatively expensive material to produce. Polymers on the other hand

can be produced in huge volumes, with a great variety of material

characteristics. MEMS devices can be made from polymers byprocesses such as injection

Metals

Metals can also be used to create MEMS elements. While metals do

not have some of the advantages displayed by silicon in terms of
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mechanical properties, when used within their limitations, metals can

exhibit very high degrees of reliability.

Metals can be deposited by electroplating,

Commenly used metals include gold, nickel,aluminium.copper,chromium,titanium,tungsten,platinium and silver

MEMS basic processes

(i) deposition(ii) pattering

(iii) etching

Deposition processes

One of the basic building blocks in MEMS processing is the ability to

deposit thin films of material with a thickness anywhere between a

few nanometres to about 100 micrometres

Patterning

Patterning in MEMS is the transfer of a pattern into a material.
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Lithography

Lithography in MEMS context is typically the transfer of a pattern into a

photosensitive material by selective exposure to a radiation source such

as light. A photosensitive material is a material that experiences a change

in its physical properties when exposed to a radiation source. If a

photosensitive material is selectively exposed to radiation (e.g. bymasking some of the radiation) the pattern of the radiation on the material

is transferred to the material exposed, as the properties of the exposed

and unexposed regions differs. This exposed region can then be removed or treated providing a mask for the

Underlying substrat.photolithography is typically used with metal ane other

Film deposition.

Etching processes

There are two types of eching processes

Wet etchingWet chemical etching consists in a selective removal of material bydipping a substrate into a solution that can dissolve it. Due to thechemical nature of this etching process, a good selectivity can oftenbe obtained, which means that the etching rate of the target material

is considerably higher than that of the mask material if selectedcarefully

Isotropic etchingEtching progresses at the same speed in all directions Long andnarrow holes in the silicon
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. The surface of these grooves can be atomically smooth if the etch is

carried out correctly, with dimensions and angles being extremely

accurate.

ELECTROCHEMICAL ECHING

Electrochemical etching (ECE) for dopant-selective removal of silicon

is a common method to automate and to selectively control etching.

An active p-n diode junction is required, and either type of dopant can

be the etch-resistant ("etch-stop") material. Boron is the most

common etch-stop dopant. In combination with wet anisotropic

etching as described above, ECE has been used successfully for

controlling silicon diaphragm thickness in commercial piezoresistive

silicon pressure sensors. Selectively doped regions can be created

either by implantation, diffusion, or epitaxial deposition of silicon.

Dry etching

(a) Xenon difluoride etching

Xenon difluride (XeF2) is a dry vapor phase isotropic etch for silicon

originally applied for MEMS in 1995 at University of California, Los

Angeles Primarily used for releasing metal and dielectric structures

by undercutting silicon, XeF2 has the advantage of a free release

unlike wet etchants. Its etch selectivity to silicon is very high, allowing

it to work with photoresist, SiO2, silicon nitride, and various metals for

masking. Its reaction to silicon is "plasmaless", is purely chemical and

spontaneous and is often operated in pulsed mode. Models of the

etching action are available, and university laboratories and various

commercial tools offer solutions using this approach

(b)Deep reactive-ion etchingDeep reactive-ion etching (DRIE) is a highly anisotropuc etch process

used to create deep, steep-sided holes and trenches in wafers ,with aspect ratios of 20:1 or more. It was developedfor microelectromechanical system (MEMS), which require thesefeatures

MEMS technology


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Micro-Electro-Mechanical Systems (MEMS) is the integrationof mechanical elements, sensors, actuators, and electronicson a common silicon substrate through microfabricationtechnology. While the electronics are fabricated using

integrated circuit (IC) process sequences (e.g., CMOS,Bipolar, or BICMOS processes), the micromechanicalcomponents are fabricated using compatible"micromachining" processes that selectively etch away partsof the silicon wafer or add new structural layers to form themechanical and electromechanical devices.

MEMS promises to revolutionize nearly every productcategory by bringing together silicon-based microelectronicswith micromachining technology, making possible therealization of complete systems-on-a-chip. MEMS is anenabling technology allowing the development of smartproducts, augmenting the computational ability of

microelectronics with the perception and control capabilitiesof microsensors and microactuators and expanding thespace of possible designs and applications.

Microelectronic integrated circuits can be thought of as the"brains" of a system and MEMS augments this decision-making capability with "eyes" and "arms", to allow


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microsystems to sense and control the environment.Sensors gather information from the environment throughmeasuring mechanical, thermal, biological, chemical, optical,and magnetic phenomena. The electronics then process the

information derived from the sensors and through somedecision making capability direct the actuators to respond bymoving, positioning, regulating, pumping, and filtering,thereby controlling the environment for some desiredoutcome or purpose. Because MEMS devices aremanufactured using batch fabrication techniques similar tothose used for integrated circuits, unprecedented levels offunctionality, reliability, and sophistication can be placed ona small silicon chip at a relatively low cost.

MEMS manufacturing technologies

Fabrication Technologies

There are three characteristic features of mems

(i)miniaturization

(ii)multiplicity

(iii)microelectronics

Miniaturization enables the production of compact, quick-response devices

Multiplicity refers to the batch fabrication inherent insemiconductor processing, which allows thousands or

millions of components to be easily and concurrentlyfabricateMEMS

Microelectronics provides the intelligence to MEMSMEMS Technology


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the successful miniaturization and multiplicity of traditional

electronics systems would not have been possible without IC

fabrication technology

MEMS sensor generations

MEMS sensor generations represent the progress made in

micro sensors technology and can be categorized as follows:

1st Generation

MEMS sensor element mostly based on a silicon structure,sometimes combined with analog amplification on a micro chip

2end generationMEMS sensor element combined with analog amplificationand analog-to-digital converter on one micro chip

3red generationFusion of the sensor element with analog amplification, analog-to-digital converter and digital intelligence for linearization andtemperature compensation on the same micro chip4th generation

Memory cells for calibration- and temperature compensation data are

added to the elements of the 3rd MEMS sensor generation.

Radiation sensitivity of microelectromechanical

system devices

the sensitivity of microelectromechanical system (MEMS) devices to

radiation is reviewed, with an emphasis on radiation levels representative of

space missions rather than of operation in nuclear reactors. As a purely

structural material, silicon has shown no mechanical degradation after

radiation doses in excess of 100 Mrad. MEMS devices,even when excluding

control/readout electronics, have, however, failed at doses of only 20 krad,

though some devices have been shown to operate correctly for doses greater

than 10 Mrad. Radiation sensitivity depends strongly on the sensing oractuation principle, device design, and materials, and is linked primarily to

the impact on device operation of radiation-induced trapped charge in

dielectrics. MEMS devices operating on electrostatic principles can be

highly sensitive to charge accumulation in dielectric layers, especially for

designs with dielectrics located between moving parts. In contrast, thermally

and electromagnetically actuated MEMS are much more radiation tolerant.


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MEMS operating on piezoresitive principles start to slowly degrade at low

doses, but do not fail catastrophically until doses of several Mrad.

Microelectromechanical Systems

(MEMS) in Radar SystemThe Air Force is supporting development of a lightweight,electronically scanning antenna using Microelectromechanical

Systems (MEMS) technology

This technology could provide significant improvements

in battlefield information superiority and airspace

The air force requires lightweight, low power, and low-costElectronically Steerable Antennas (ESA) such as thoseneeded by high-performance Airborne Moving Target

Indicator (AMTI) and Surface Moving Target Indicator (SMTI)radars. Rapid beam scanning, beam agility, the performanceof diverse functions such as multiple target tracking and firecontrol, reduced Radar Cross Section (RCS), and reducedphysical profile are some of the numerous performancebenefits to systems employing an ESA. These radar systemsrequire a large power-aperture product, but must belightweight enough for aerostats and Airships For the firsttime, a lightweight, electronically scanning antenna usingMicroelectromechanical Systems (MEMS) technologyhas been used for airborne and surface target detection,while interfaced with an existing radar system. Thedemonstration ESA contains 25,000 MEMS devices,electronically scans 120 degrees and operates over a 1-GHzbandwidth at X-band. The0.4 square meter antenna wasbuilt to demonstrate feasibility of much larger antennas,exceeding 8 square meters. Much of the enhanced antennaperformance is attributed to the employment of MEMSswitches instead of traditional semiconductor-based

switching technologies. The MEMS switches manufacturedbyRadant MEMS, Inc. have a volume of only 1.5 cubicmillimeters and are produced by wafer capping of a micro-mechanicalswitch mechanism that travels less than 1micrometer in10 microseconds.


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Applications of MEMS

Here are some examples of MEMS technology:

A. Pressure Sensors

MEMS pressure microsensors typically have a flexiblediaphragm that deforms in the presence of a pressure

difference. The deformation is converted to an electricalsignal appearing at the sensor output. A pressure sensor canbe used to sense the absolute air pressure within the intakemanifold of an automobile engine, so that the amount of fuelrequired for each engine cylinder can be computed. In thisexample, piezoresistors are patterned across the edges of aregion where a silicon diaphragm will be micromachined. The
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substrate is etched to create the diaphragm. The sensor dieis then bonded to a glass substrate, creating a sealedvacuum cavity under the diaphragm. The die is mounted ona package, where the topside of the diaphragm is exposed

to the environment. The change in ambient pressure forcesthe downward deformation of the diaphragm, resulting in achange of resistance of the piezoresistors. On-chipelectronics measure the resistance change, which causes acorresponding voltage signal to appear at the output pin ofthe sensor package

ersB.ACCELEROMETER

Accelerometers are acceleration sensors. An inertial masssuspended by springs is acted upon by acceleration forcesthat cause the mass to be deflected from its initial position.This deflection is converted to an electrical signal, whichappears at the sensor output. The application of MEMS


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technology to accelerometers is a relatively newdevelopment.

One such accelerometer design is discussed by DeVoe and

Pisano (2001). It is a surfacemicromachined piezoelectric accelerometer employing a zincoxide (ZnO) active piezoelectric film. The design is a simplecantilever structure, in which the cantilever beam servessimultaneously as proof mas and sensing element. One ofthe fabrication approaches developed is a sacrificial oxideprocess based on polysilicon surface micromachining, withthe addition of a piezoelectric layer atop the polysilicon film.In the sacrificial oxide process, a passivation layer of silicon

dioxide and low-stress silicon nitride is deposited on a baresilicon wafer, followed by 0.5 micron of liquidphase chemical vapor deposited (LPCVD) phosphorous-doped polysilicon. Then, a 2.0-micron layer ofphosphosilicate glass (PSG) is deposited by LPCVD andpatterned to define regions where the accelerometerstructure will be anchored to the substrate. The PSG filmacts as a sacrificial layer that is selectively etched at the endto free the mechanical structures. A second layer of 2.0-

micron-thick phosphorus-doped polysilicon is deposited viaLPCVD on top of the PSG, and patterned by plasma etchingto define the mechanical accelerometer structure. This layeralso acts as the lower electrode for the sensing film. A thinlayer of silicon nitride is next deposited by LPCVD, and actsas a stress-compensation layer for balancing the highlycompressive residual stresses in the ZnO film. By varyingthe thickness of the Si3N4 layer, the accelerometer structuremay be tuned to control bending effects resulting from the

stress gradient through the device thickness. A ZnO layer isthen deposited on the order of 0.5 micron, followed bysputtering of a 0.2-micron layer of platinum (Pt) depositedto form the upper electrode. A rapid thermal anneal isperformed to reduce residual stresses in the sensing film.Afterwards, the Pt, Si3N4, and ZnO layers are patterned in asingle ion milling etch step, and the devices are then


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released by passivating the ZnO film with photoresist, andimmersing the wafer in buffered hydrofluoric acid, whichremoves the sacrificial PSG layer

C.Inertial Sensors

Inertial sensors are a type of accelerometer and are one ofthe principal commercial products that utilize surfacemicromachining. They are used as airbag-deploymentsensors in automobiles, and as tilt or shock sensors. Theapplication of these accelerometers to inertial measurementunits(IMUs) is limited by the need to manually align andassemble them into three-axis systems, and by the resultingalignment tolerances, their lack of in-chip analog-to-digitalconversion circuitry, and their lower limit of sensitivity. Theaccelerometer was designed for the integratedMEMS/CMOS technology. This technology involves amanufacturing technique where a single-level (plus a secondelectrical interconnect level) polysilicon micromachiningprocess is integrated with 1.25-micron CMOS.

D.MicroenginesA three-level polysilicon micromachining process has

enabled the fabrication of devices with increased degrees ofcomplexity. The process includes three movable levels ofpolysilicon, each separated by a sacrificial oxide layer, plus astationary level. Operation of the small gears at rotationalspeeds greater than 300,000 rpm has been demonstrated.Microengines can be used to drive the wheels ofmicrocombination locks. They can also be used incombination with a microtransmission to drive a pop-upmirror out of a plane. This device is known as a micromirror.

E.MEMS thermal actuator

A MEMS thermal actuator is a micromechanical device that typicallygenerates motion by thermal expansion amplification. A smallamount of thermal expansion of one part of the device translates to alarge amount of deflectionof the overall device


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Usually fabricated out of doped single crystal silicon or poly silicon ,the increase in temperature can be achieved internally by electricalsensitive haeting or externally by a heat source capable of locallyintroducing heat.

F.Electrostatic motor

An electrostatic motor or capacitor motor is a type of electric

motor based on the attraction and repulsion of electric charge.

Usually, electrostatic motors are the dual of conventional coil-based

motors. They typically require a high voltage power supply, although

very small motors employ lower voltages. Conventional electric

motors instead employ magnetic attraction and repulsion, and require

high current at low voltages. In the 1750s, the first electrostatic

motors were developed by Benjamin Franklin andAndrew Gordon.

Today the electrostatic motor finds frequent use in micro-mechanical

(MEMS) systems where their drive voltages are below 100 volts, and

where moving charged plates are far easier to fabricate than coils

and iron cores. Also, the molecular machinery which runs living cells

is often base d on linear and rotary electrostatic motors

Some other applications

MEMS IC fabrication technologies have also allowed themanufacture of microtransmissions using sets of small andlarge gears interlocking with other sets of gears to transferpower.

A recently developed MicroStar cross-connect fabricdeveloped by Bell Labs a micro-optoelectromechanical

system device, is based on MEMS technology. The mostpervasive bottlenecks for communications carriers are theswitching and cross-connect fabrics that switch,route, multiplex, demultiplex, and restore traffic in opticalnetworks. The optical transmission systems moveinformation as photons, but switching and cross-connectfabrics until now have been largely electronic, requiring


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costly and time-consuming bandwidth-limiting optical-to-electronic-to-optical conversions at every networkconnection and cross point. MicroStar is composed of 256mirrors, each one 0.5 mm in diameter, spaced 1 mm apart,

and covering less than 1 square inch of silicon. The mirrorssit within the router so that only one wavelength canilluminate any one mirror. Each mirror can tilt independentlyto pass its wavelength to any of 256 input and output fibers.The mirror arrays are made using a self-assembly processthat causes a frame around each mirror to lift from thesilicon surface and lock in place, positioning the mirrors highenough to allow a range of movement. MicroStar is part ofLucent Technology's Lambda Router cross-connect system

aimed at helping carriers deliver vast amounts of dataunimpeded by conventional bottlenecks.

As a final example, MEMS technology has been used infabricating vaporization microchambers for vaporizing liquidmicrothrusters for nanosatellites. The chamber is part of amicrochannel with a height of 2-10 microns, made usingsilicon and glass substrates. The nozzle is fabricated in thesilicon substrate just above a thin-film indium tin oxide

heater deposited on glass.

The Future

Each of the three basic microsystems technology processeswe have seen, bulk micromachining, sacrificial surfacemicromachining, and micromolding/LIGA, employs adifferent set of capital and intellectual resources. MEMSmanufacturing firms must choose which specificmicrosystems manufacturing techniques to invest in [

MEMS technology has the potential to change our daily livesas much as the computer has. However, the material needsof the MEMS field are at a preliminary stage. A thoroughunderstanding of the properties of existing MEMS materials


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is just as important as the development of new MEMSmaterials.

Future MEMS applications will be driven by processes

enabling greater functionality through higher levels ofelectronic-mechanical integration and greater numbers ofmechanical components working alone or together to enablea complex action. Future MEMS products will demand higherlevels of electrical-mechanical integration and more intimateinteraction with the physical world. The high up-frontinvestment costs for large-volume commercialization ofMEMS will likely limit the initial involvement to largercompanies in the IC industry. Advancing from their success

as sensors, MEMS products will be embedded in larger non-MEMS systems, such as printers, automobiles, andbiomedical diagnostic equipment, and will enable new andimproved systems

MEMS devices

Geophone


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The term geophone derives from the Greek word "geo" meaning"earth " and "phone" meaning "sound"

MEMS TechnologyA geophone is a device which converts ground movement

(displacement) into voltage, which may be recorded at a recordingstation. The deviation of this measured voltage from the base line iscalled the seismic response and is analyzed for structure of the earthGeophones have historically been passive analog devices andtypically comprise a spring-mounted magnetic mass moving within awire coil to generate an electrical signal. Recent designs have beenbased on microelectromechanicalsystms technology whichgenerates an electrical response to ground motion through an activefeedback circuit to maintain the position of a small piece of silicon

The response of a coil/magnet geophone is proportional to groundvelocity, while microelectromechanical systems

devices usually respond proportional to acceleration.Microelectromechanical systems have a much higher noise level (50dB velocity higher) than geophones and can only be used in strongmotion or active seismic applications

microturbine technology

The components of any turbine engine: the gas compressor,

the combustion chamber, and the turbine rotor itself, are fabricated

from etched silicon, much like integrated circuits. The technology

holds the promise of ten times the operating time of a battery of the

same weight as the micropower unit, and similar efficiency to

large utility gas turbinesa micro generator 10 mm wide, which spins a magnet above an

array of coils fabricated on a silicon chip. The device spinsat 100,000 revolutions per minute, and produces 1.1 wattsof electrical power, sufficient to operate acell phone . Theirgoal is to produce 20 to 50 watts, sufficient to power a laptopcomputer.


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MICROPHONEA mircroelectromechnical system microphone, comprising:a

first electrode, disposed on a substrate and having a firstflexible portion;a second electrode, disposedfirst dielectric layer, partially disposed between the firstelectrode and the second electrode so as to suspend the firstflexible portion between the first electrode and the substrate

USES OFMEMSMICRO ELECTRO MECHANICAL Sinformation syst YSTEMems used to be embedded in computers

at fixed locations. Now they are also found in nearlyeveryone's hands and pockets, thanks to miniaturization ofelectromechanical systems.Using the fabrication techniques and materials ofmicroelectronics as a basis, micro electro mechanicalsystems (MEMS) processes

are shrinking machines to microscopic dimensions. .

Smallest motors.

as a basis, micro electro mechanical systems (MEMS) processes

Already the world's smallest motors have rotors that are lessthan the diameter of a human hair. These motors arepowering optical switches, valves and airbag deploymentsensors

New uses

Widely used, MEMS devices and their use will continue toexpand. Already, cars, fighter aircraft, printers and munitions useMEMS devices, and the devices account for a relatively smallfraction of their cost, size and weight.

MEMS devices and the smart products they enable will createnew opportunities for perceiving and controlling our work and life
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environments and will increasingly be the performancedifferentiator for both defense and commercial systems.

While MEMS devices will be a relatively small fraction of the cost,size and weight of these systems, MEMS will be critical to theiroperation, reliability and affordability

Advances in IC technology in the last decade have broughtabout corresponding progress in MEMS fabricationprocesses. Manufacturing processes allow for the monolithicintegration of microelectromechanical structures withdriving, controlling, and signal-processing electronics. Thisintegration promises to improve the performance ofmicromechanical devices as well as reduce the cost ofmanufacturing, packaging, and instrumenting these device


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